Today's announcement is a huge setback in efforts to fight the pandemic, which emerged in China last December and has killed over 1.5 million people worldwide.
Sanofi and GSK said the delay in their adjuvanted recombinant protein-based Covid-19 vaccine programme was to "improve immune response in older adults."
The vaccine's potential availability had been pushed back "from mid-2021 to Q4 2021," they said in a statement.
American pharmaceutical giant Pfizer and its German partner BioNTech have said their vaccine had proven 90% effective in preventing Covid-19 infections in ongoing Phase 3 trials involving more than 40,000 people.
The vaccine candidate, developed by Sanofi in partnership with GSK, is based on technology that Sanofi has used to produce seasonal influenza vaccines and on immunological agents developed by GSK.
The hunt for a vaccine has brought up questions on whether unexpected safety issues may arise when the number of people vaccinated grows to millions and possibly billions of people.
Sanofi, GSK delay COVID-19 vaccine programhttps://t.co/pViiJ0I305#Teletrader#Roboinfo0.120#Robotex group
— Robotex group (@Robotexgroup) December 11, 2020
More than one vaccine needed
Another unknown is whether more side effects will emerge with longer follow-up, how long the vaccine remains effective, whether it will limit transmission and how it will work in children, pregnant women, and immunocompromised patients.
Both Russia and China have already begun inoculation campaigns with domestically produced vaccines despite far less vetting as several other vaccines are being developed in the West.
Thomas Triomphe, Executive Vice President and Head of Sanofi Pasteur has indicated that "No single pharma company can make it alone; the world needs more than one vaccine to fight the pandemic."
Roger Connor, President of GSK Vaccines added: "The results of the study are not as we hoped. Based on previous experience and other collaborations, we are confident that GSK's pandemic adjuvant system, when coupled with a Covid-19 antigen, can elicit a robust immune response."
The companies plan a Phase 2b study expected to start in February.
If the data is positive, a global Phase 3 study could start in the second quarter of next year.
